1. Field of Invention
The invention relates to a safety insert for extra-corporeal circuits, in particular a transducer protector for preventing contamination of a pressure gauge on the extra-corporeal circuit.
2. Description of the Prior Art
In therapeutic treatments which require an extra-corporeal circulation system, such as haemodialysis, the arterial and venous pressure in the extra-corporeal circuit must be constantly monitored. This is achieved in a manner known per se by means of pressure transducers connected to the main circuit via suitable branch pipes. In an equally known manner, a safety insert or transducer protector is positioned between the pipe and the pressure transducer in order to avoid any possible contact between the patient's blood and the machine (artificial kidney). In fact, the extra-corporeal circuit is made of disposable material, while the artificial kidney as a whole must, of necessity, be continuously reused.
The transducer protector is formed, in a manner known per se, by means of a plastic shell enclosing a hydrophobic gas permeable membrane. Each side of the shell comprises a tubular connector. A first tubular connector is designed to be connected to the branch pipe, while the other tubular connector is designed to be connected to the pressure transducer.
Due to pressure fluctuations, the patient's blood can enter the branch pipe and the first tubular connector. In such a case, the membrane is intended to stop the blood flow so as to prevent contamination of the machine. In a minor number of cases, the membrane can leak or even break and a contamination of the machine can occur without any notice of the service personnel.
In order to increase the overall safety margin of the system, also such a rare incident should be avoided. Double transducer protectors have been provided for this reason.
According to its first version, the double transducer protector simply comprises two membranes in series. Such device is very simple, but its effectiveness in reducing the risk of contamination relies on a merely statistical basis. A transducer protector of this type is disclosed in EP 1 605 990.
Other versions of double transducer protectors have two membranes in series and means to detect the presence of a contaminant between the membranes. Such devices are adapted to alert the service personnel in case of leakage of the first membrane, thus actually increasing the overall safety margin. In turn, such devices are quite complex and require additional components for the system. Transducer protectors of this type are disclosed in EP 1 547 630 and in EP 1 728 526.